Health literacy, numeracy, and interpretation of graphical breast cancer risk estimates

Abstract

Objective

Health literacy and numeracy are necessary to understand health information and to make informed medical decisions. This study explored the relationships among health literacy, numeracy, and ability to accurately interpret graphical representations of breast cancer risk.

Methods

Participants (N = 120) were recruited from the Facing Our Risk of Cancer Empowered (FORCE) membership. Health literacy and numeracy were assessed. Participants interpreted graphs depicting breast cancer risk, made hypothetical treatment decisions, and rated preference of graphs.

Results

Most participants were Caucasian (98%) and had completed at least one year of college (93%). Fifty-two percent had breast cancer, 86% had a family history of breast cancer, and 57% had a deleterious BRCA gene mutation. Mean health literacy score was 65/66; mean numeracy score was 4/6; and mean graphicacy score was 9/12. Education and numeracy were significantly associated with accurate graph interpretation (r = 0.42, p < 0.001 and r = 0.65, p < 0.001, respectively). However, after adjusting for numeracy in multivariate linear regression, education added little to the prediction of graphicacy (r² = 0.41 versus 0.42, respectively).

Conclusion

In our highly health-literate population, numeracy was predictive of graphicacy.

Practice implications

Effective risk communication strategies should consider the impact of numeracy on graphicacy and patient understanding.

Introduction

Essential to informed patient decision-making is the ability to understand numerically and graphically presented health information. Previous studies have shown that health literacy [1], [2], numeracy [2], [3], and graph design [4], [5] may influence patient understanding of health communications. Comprehension of prevention and risk information is important in decision-making for women who carry a BRCA mutation given the magnitude of the associated risks of breast and ovarian cancer. BRCA mutations confer an 85% lifetime of breast cancer [6], [7] and a second primary breast cancer risk of approximately 50% [8] as well as a lifetime risk for ovarian cancer of about 15–50% [6], [7], [9]. Women who carry a BRCA mutation may consider bilateral mastectomy and/or bilateral salpingo-oophorectomy as risk-reduction strategies [10]. In order to make a fully informed decision regarding risk management, it is important that these women understand their cancer risks as well as the risk-reduction impact and quality of life outcomes of each surgical intervention. No studies to date have explored the ability of BRCA+ women to interpret graphically presented risk information.

The United States Department of Health and Human Services has defined health literacy as “the degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions” [11]. As such, health literacy has been shown to be a critical component of meaningful cancer risk communication, treatment and screening compliance, informed consent, and overall patient health [1], [12], [13], [14], [15], [16]. Individuals with low health literacy scores often do not understand basic cancer prevention, or diagnosis and treatment terminology such as screening, colon, tumor, lesion, and cure, which may contribute to a lack of adherence to potentially lifesaving screening recommendations [17].

Numeracy has been defined as, “the degree to which individuals have the capacity to access, process, interpret, communicate, and act on numerical, quantitative, graphical, biostatistical, and probabilistic health information needed to make effective health decisions” [18]. Until recently, numeracy was considered and often measured as a component of health literacy. However, several studies have shown that numeracy is a separate proficiency from literacy and that health numeracy is a significant and distinctive aspect of health knowledge and communication [2], [18], [19], [20], [21].

Patient numeracy and the presentation of probabilistic health outcome information impact health care in diverse areas from prevention to treatment [22], [23], [24], [25]. Although patients report higher trust and comfort with their health care provider when numerical data are included [26], they may not always understand the given data. In a study of 463 highly educated participants, about 40% could not solve a basic probability problem or convert a percentage to a proportion [27]. Therefore, health care providers cannot assume that well-educated patients are numerate when discussing treatment decisions and risk. In another study, less numerate women were less likely to accurately assess the reduction in breast cancer death from screening mammography [28]. Additionally, studies suggest that innumerate individuals are more likely than their numerate peers to inaccurately understand their health risks [3] and are more likely to have inaccurate perceptions of the health consequences of cancer screening, surveillance, and treatment choices [19], [29].

Graphicacy has been defined as “the ability to understand and present information in the form of sketches, photographs, diagrams, maps, plans, charts, graphs, and other non-textual, two-dimensional formats” [30]. Graphical representations of risk have been shown to improve patient understanding, informed consent, and decision-making accuracy [5], [31], particularly for those individuals with low levels of numeracy [28], [32].

Several studies have tested the effectiveness of various graphical formats. The presentation of health care data in simple forms, such as single line graphs [33], bar graphs [34] or frequency graphs showing highlighted human figures [4], has been shown to improve patient understanding and influence treatment decisions. A bar graph tailored to women's breast cancer risk improved accuracy of self-described risk among women with a family history of breast cancer [34]. Another study found that using a frequency diagram plus a bar graph improved risk perception accuracy more than by using a bar graph alone [35]. A focus group study concluded that frequency graphs are contextual, easy to understand, and meaningful; however, when compared to participants with more formal education, participants with less education more often perceived their risk of breast cancer to be erroneously high when using human figure frequency graphs rather than bar graphs [4]. In addition, some participants found that bar graphs were a more helpful format for the comparison of multiple risks [4]. Another study showed that utilizing two complimentary graphs, a frequency graph along with a bar graph, improved risk perception accuracy more than by using a single graph [35]. In studies considering patient understanding and treatment choice by comparing risk communication formats, researchers identified that graphical format alone influenced risk perception and treatment decisions [36], [37].

Thus, graphicacy is considered a key patient skill utilized for breast cancer risk communication [38], yet, little is known about the relationship of graphicacy to health literacy and numeracy. Therefore, the aim of this study was to examine the relationship between literacy, numeracy, and graphicacy, in the context of breast cancer risk communication and decision-making about risk-reducing surgery for high risk patients.